Is it possible to extend block elements/modifiers in less?

Question

css

For example, there is

.btn {
    display: inline-block;
    &_round {
        border-radius: 50%;
    }
}

How can you extend with a modifier?

Answer 1

It's not very clear what you want to end up with. You can extend.

.btn:extend(.someclass) {
     display: inline-block;
    &_round {
        border-radius: 50%;
    }
}